Objective-C和Swift的转换速查手册（推荐）

//Objective-CNSInteger score = 556;//NSString *name = @"Taylor";//BOOL loggedIn = NO;

//Swiftvar score = 556//var name = "Taylor"//var loggedIn = false

//Objective-Cconst NSInteger score = 556;//NSString * const name = @"Taylor";//const BOOL firstRun = YES;//Objective-C中常量用的很少

//Swiftlet score = 556//let name = "Taylor"//let firstRun = true//Swift中常量很常见

//Objective-CNSArray *grades = @[@90, @85, @97];//NSArray *names = @[@"Taylor", @"Adele", @"Justin"];

//Swiftlet grades = [90, 85, 97]//let names = ["Taylor", "Adele", "Justin"]

//Objective-CNSMutableArray *array = [NSMutableArray new];//[array addObject:[NSValue valueWithRect:CGRectMake(0, 0, 32, 64)]];//在添加到集合前，值类型有对应的引用类型

//Swiftvar array = [CGRect]()//array.append(CGRect(x: 0, y: 0, width: 32, height: 64))

//Objective-CNSDictionary *houseNumbers = @{ @"Paul": @7, @"Jess": @56, @"Peter": @332 };

//Swiftlet houseNumbers = ["Paul": 7, "Jess": 56, "Peter": 332]

//Objective-Ctypedef NS_ENUM(NSInteger, ShapeType) { kCircle, kRectangle, kHexagon};

//Swiftenum ShapeType: Int { case circle case rectangle case hexagon}

//Objective-CNSString *first = @"Hello, ";NSString *second = [first stringByAppendingString:@" world!"];

//Swiftlet first = "Hello, "let second = first + "world!"

//Objective-CNSInteger rating = 4;rating++;rating += 3;

//Swiftvar rating = 4rating += 1rating += 3

//Objective-CNSString *account = @"twostraws";NSString *str = [NSString stringWithFormat:@"Follow me on Twitter: %@", account];

//Swiftlet account = "twostraws"let str = "Follow me on Twitter: /(account)"

//Objective-CNSString *username = @"twostraws";NSLog(@"Username is %@", username);

//Swiftlet username = "twostraws"print("Username is /(username)")

//Objective-CNSInteger result = 86;if (result >= 85) { NSLog(@"You passed the test!");} else { NSLog(@"Please try again.");}

//Swiftlet result = 86if result >= 85 { print("You passed the test!")} else { print("Please try again.")}

//Objective-Cfor (NSInteger i = 0; i < 100; ++i) { NSLog(@"This will be printed 100 times.");}

//Swiftfor _ in 0 ..< 100 { print("This will be printed 100 times.")}

//Objective-CNSArray *companies = @[@"Apple", @"Facebook", @"Twitter"];for (NSString *name in companies) { NSLog(@"%@ is a well-known tech company.", name);}

//Swiftlet companies = ["Apple", "Facebook", "Twitter"]for name in companies { print("/(name) is a well-known tech company.")}

//Objective-CNSInteger rating = 8;switch (rating) { case 0 ... 3: NSLog(@"Awful"); break; case 4 ... 7: NSLog(@"OK"); break; case 8 ... 10: NSLog(@"Good"); break; default: NSLog(@"Invalid rating.");}//很多人不知道Objective-C有范围支持，所以你也许看到二选一的语法

//Swiftlet rating = 8switch rating {case 0...3: print("Awful")case 4...7: print("OK")case 8...10: print("Good")default: print("Invalid rating.")}//Swift不会fall through案例，除非你使用fallthrough关键字

//Objective-C- (void)printGreeting { NSLog(@"Hello!");}[self printGreeting];

//Swiftfunc printGreeting() { print("Hello!")}printGreeting()

//Objective-C- (NSString*)printGreeting { return @"Hello!";}NSString *result = [self printGreeting];

//Swiftfunc printGreeting() -> String { return "Hello!"}let result = printGreeting()

//Objective-C- (NSString*)printGreetingFor:(NSString*)user { return [NSString stringWithFormat:@"Hello, %@!", user];}NSString *result = [self printGreetingFor:@"Paul"];//第一个参数的名称需要为方法名的一部分

//Swiftfunc printGreeting(for user: String) -> String { return "Hello, /(user)!"}let result = printGreeting(for: "Paul")

//Objective-C- (NSString*)printGreetingFor:(NSString*)user withAge:(NSInteger)age { if (age >= 18) {  return [NSString stringWithFormat:@"Hello, %@! You're an adult.", user]; } else {  return [NSString stringWithFormat:@"Hello, %@! You're a child.", user]; }}NSString *result = [self printGreetingFor:@"Paul" withAge:38];

//Swiftfunc printGreeting(for user: String, age: Int) -> String { if age >= 18 {  return "Hello, /(user) You're an adult." } else {  return "Hello, /(user)! You're a child." }}let result = printGreeting(for: "Paul", age: 38)

//Objective-C- (NSDictionary*)loadAddress { return @{  @"house": @"65, Park Street",  @"city": @"Bristol",  @"country": @"UK" };}NSDictionary*address = [self loadAddress];NSString *house = address[@"house"];NSString *city = address[@"city"];NSString *country = address[@"country"];//Objective-C不支持元祖(tuple),所以用字典或数组替代

//Swiftfunc loadAddress() -> (house: String, city: String, country: String) { return ("65, Park Street", "Bristol", "UK")}let (city, street, country) = loadAddress()

//Objective-Cvoid (^printUniversalGreeting)(void) = ^{ NSLog(@"Bah-weep-graaaaagnah wheep nini bong");};printUniversalGreeting();

//Swiftlet universalGreeting = { print("Bah-weep-graaaaagnah wheep nini bong")}universalGreeting()

//Objective-CNSString* (^getUniversalGreeting)(void) = ^{ return @"Bah-weep-graaaaagnah wheep nini bong";};NSString *greeting = getUniversalGreeting();NSLog(@"%@", greeting);

//Swiftlet getUniversalGreeting = { return "Bah-weep-graaaaagnah wheep nini bong"}let greeting = getUniversalGreeting()print(greeting)

//Objective-CNSString* (^getGreeting)(NSString *) = ^(NSString *name) { return [NSString stringWithFormat:@"Live long and prosper, %@.", name];};NSString *greeting = getGreeting(@"Paul");NSLog(@"%@", greeting);

//Swiftlet getGreeting = { (name: String) in return "Live long and prosper, /(name)."}let greeting = getGreeting("Paul")print(greeting)

//Objective-C@interface MyClass : NSObject@end@implementation MyClass@end

//Swiftclass MyClass: NSObject {}//推荐使用结构代替类，这样也许不需要从NSObject继承了

//Objective-C@interface User : NSObject@property (nonatomic, copy) NSString *name;@property (nonatomic, assign) NSInteger age;@end@implementation User@end

//Swiftclass User { var name: String var age: Int  init(name: String, age: Int) {  self.name = name  self.age = age }}//Swift要求进行初始化，给这些属性默认值

//Objective-C//在头文件中@interface User : NSObject@property (nonatomic, copy) NSString *name;@end//在执行文件中@interface User()@property (nonatomic, assign) NSInteger age;@end@implementation User@end//Objective-C实际上并不支持私有属性，通常都用这种变通方式

//Swiftclass User { var name: String private var age: Int  init(name: String, age: Int) {  self.name = name  self.age = age }}

//Objective-C@interface Civilization : NSObject- (NSInteger)getMeaningOfLife;@end@implementation Civilization- (NSInteger)getMeaningOfLife { return 42;}@end

//Swiftclass Civilization { func getMeaningOfLife() -> Int {  return 42 }}

//Objective-C@interface Civilization : NSObject+ (NSInteger)getMeaningOfLife;@end@implementation Civilization+ (NSInteger)getMeaningOfLife { return 42;}@end//差别很小，用+而不是-

//Swiftclass Civilization { class func getMeaningOfLife() -> Int {  return 42 }}//Swift也支持静态方法——它不会在子类中被覆盖

//Objective-C@interface NSString (Trimming)- (NSString*)trimmed;@end@implementation NSString (Trimming)- (NSString*)trimmed { return [self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];}@end

//Swiftextension String { func trimmed() -> String {  return trimmingCharacters(in: .whitespacesAndNewlines) }}

//Objective-Cif ([object isKindOfClass:[YourClass class]]) { NSLog(@"This is a YourClass.");}

//Swiftif object is YourClass { print("This is a YourClass.")}

//Objective-CDog *poodle = (Dog*)animalObject;

//Swiftlet poodle = animalObject as? Dog//let poodle = animalObject as! Dog//如果不是一个dog，前者会把poodle设为nil，后者则会崩溃

//Objective-Cdispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSLog(@"Running in the background...");  dispatch_async(dispatch_get_main_queue(), ^{  NSLog(@"Running back on the main thread"); });});

//SwiftDispatchQueue.global().async { print("Running in the background...")  DispatchQueue.main.async {  print("Running on the main thread") }}